The detection of the rich p-mode spectrum and asteroseismology of Przybylski's star
Aims: We investigate the oscillation spectrum of the mostchemically-peculiar star in the sky, the rapidly-oscillating magnetic(roAp) star HD 101065. Methods: High-precisionradial velocity (RV) measurements, spanning four consecutive nights on3-6 March, 2004, were obtained with the HARPS echelle-spectrometer atthe ESO 3.6-m telescope, and photometric data were acquired during 6nights of observations at the 24-inch telescope of Siding SpringObservatory. The RVs were measured using all spectral lines in thewavelength range 4400-5100 Å. Results: We detected a richspectrum of oscillation modes with semi-amplitudes ranging between 217 ms-1 and 1.6 m s-1. These belong to the completespectrum of high-order, low ? = 0-2 modes, having a large spacing ofoverline? ? = 64.07 ± 0.9 ?Hz. We calculated thenonadiabatic frequencies of axisymmetric high-order p-modes formain-sequence models with dipole magnetic fields of two chemicalcompositions (X,Z)= (0.7,0.02) and (X,Z) = (0.695,0.025). The formercomposition provided the best fit model and yielded stellar parametersof mass, M=1.525 ± 0.025 M_?, age = (1.5 ± 0.1)× 109 yr, effective temperature log T_e=3.821 ±0.006, luminosity log L/L?= 0.797 ± 0.026,surface gravity log g=4.06 ±0.04, and polar magnetic fieldstrength, Bp = 8.7± 0.3 kG. We are able to identify the modes ofall detected oscillation frequencies. The photometric U and B lightcurves have maxima that precede the RV maximum by 0.16-0.19 in phase.Based on observations made on the 3.6 m Telescope at La Silla of theEuropean Southern Observatory under program 072.D-0286.
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